This invention relates to a method of sanding, especially the sanding of items of wood, in a sanding machine, where the items are conveyed on a plane such as a vacuum plane, while at the same time the surface of the items is swept by sanding tools, said sanding tools comprising a number of sanding rollers, each secured to a spindle, and where the spindles are mounted radially outwards from a drive, and in such a manner that the individual sanding rollers rotate both around the spindle axes and around an axis of rotation which extends at right-angles to the spindle axes, and also a machining apparatus for use in the execution of the method.
Methods of this kind are known, e.g. from DK published specification no. 156,703, and are used especially in the sanding of the surfaces of items of wood, which while secured on a plane are machined by sanding rollers during their composite movement over the upper surfaces.
In order to be able to machine items with irregular surfaces such as recesses, profiles and flutes, the machining must be effected as carefully as possible out of regard for the preservation of the sharp edges, but at the same time it must be effective enough to ensure that all surfaces, including the irregular surfaces, are machined to the necessary degree.
For this purpose, the sanding rollers preferably used are made up of equally-long, flexible sanding threads or sanding bands which extend radially from a core, and which constitute the sanding roller.
Such sanding rollers are secured to individual spindles which are mounted on a drive in such a manner that the rollers project outwards from the drive like spoke from a hub.
Mounted in this way, the sanding rollers can be made to rotate on their spindles, while at the same time all of the sanding rollers simultaneously rotate around an axis which extends at right-angles to the sanding spindles.
Items placed on the feed belt are now able to be fed in under the sanding rollers, which by their composite movement will machine the items from several directions.
In correctly dimensioned machines, this method results in satisfactory sanding, but there are difficulties with items which are placed on the feed belt in such a manner that they pass closely by the axis of rotation of the sanding rollers, and in the area of the rollers' outer turning track.
In these positions, the predominant direction of sanding executed by the rollers will be the transverse and the longitudinal respectively in relation to the feeding direction of the belt. Furthermore, the ends of the sanding rollers have a relatively high speed of rotation, whereby the result of the sanding can be inferior in the outer positions.
Therefore, if the need exists for a completely perfect surface finish, the items must be sanded again or placed in another position, or use must be made of machines which are provided with several sanding heads which can be mounted in a staggered manner in relation to the feeding direction of the belt.
However, these solutions are not expedient, since they either require an extra pass through the machine, and herewith sanding time, or larger machines with several sanding systems which are both more expensive and require more maintenance.